| Year | Title | Role | Notes |
| 1967 | The Dating Game | Contestant | Selected as the "Winning Bachelor" |
| 1968 | Crazy World, Crazy People | Various characters | TV special |
| 1970 | Dan August | Coley Smith | Episode: "Quadrangle for Death" |
| 1971 | Hawaii Five-O | Ryan Moore, Mike Welles | 2 episodes |
| 1972–1976 | The Waltons | Rev. Matthew Fordwick | Recurring role (18 episodes) |
| 1973 | Medical Center | Ronnie | Episode: "End of the Line" |
| Bachelor-at-Law | Ben Sykes | Unsold pilot |
| M*A*S*H | Pvt. Carter | Episode: "Deal Me Out" |
| 1974 | Kojak | Kenny Soames | Episode: "Deliver Us Some Evil" |
| Owen Marshall, Counselor at Law | Greg | Episode: "To Keep and Bear Arms" |
| The Bob Newhart Show | Dave | Episode: "Sorry, Wrong Mother" |
| 1975 | Movin' On | Casey | Episode: "Landslide" |
| Rhoda | Vince Mazuma | Episode: "Chest Pains" |
| Mannix | Cliff Elgin | Episode: "Hardball" |
| Great Performances | Richard | Episode: "Who's Happy Now?" |
| The Bob Crane Show | Hornbeck | Episode: "Son of the Campus Capers" |
| Petrocelli | John Oleson | Episode: "Chain of Command" |
| Barnaby Jones | Joe Rockwell | Episode: "The Price of Terror" |
| The Streets of San Francisco | John 'Johnny' Steiner | Episode: "Murder by Proxy" |
| The Night That Panicked America | Walter Wingate | TV film |
| The Mary Tyler Moore Show | Reverend Chatfield | Episode: "Ted's Wedding" |
| The Rookies | Hap Dawson | Episode: "Reluctant Hero" |
| 1976 | Starsky & Hutch | Tom Cole | Episode: "The Hostages" |
| Doc | Jeff, George | Episode: "A Little Bit of Soap" |
| Rhoda | Jerry Blocker | Episode: "Attack on Mr. Right" |
| Phyllis | Paul Jameson | Episode: "The New Job" |
| 1977–1984 | Three's Company | Jack Tripper | Lead role (174 episodes) |
| 1977 | The Love Boat | Dale Riley | Episode: "Oh, Dale" |
| Tattletales | Himself (panelist) | Syndication |
| 1978 | Ringo | Marty Flesh | TV film |
| Leave Yesterday Behind | Paul Stallings |
| $25,000 Pyramid | Himself (panelist) | Syndication |
| 1979 | The Ropers | Jack Tripper | Episode: "The Party" |
| 1980 | The Associates | Chick | Episode: "The Censors" |
| The Comeback Kid | Bubba Newman | TV film |
| John Ritter: Being of Sound Mind and Body | Himself, Various Characters | TV special |
| 1981 | Insight | Frankie | Episode: "Little Miseries" |
| 1982 | Pray TV | Tom McPherson | TV film |
| In Love with an Older Woman | Robert Christenberry |
| The Fantastic Miss Piggy Show | Himself (guest star) | TV special |
| 1983 | Sunset Limousine | Alan O'Black | TV film |
| The Love Boat | Ben Cummins | Episode: "The Emperor's Fortune" |
| 1984 | Love Thy Neighbor | Danny Loeb | TV film |
| Pryor's Place | Himself (guest star) | Episode: "The Showoff" |
| 1984–1985 | Three's a Crowd | Jack Tripper | Lead role (22 episodes) |
| 1985 | Letting Go | Alex Schuster | TV film |
| 1986 | Unnatural Causes | Frank Coleman |
| A Smoky Mountain Christmas | Judge Harold Benton |
| Life with Lucy | Himself (guest star) | Episode: "Lucy Makes a Hit with John Ritter" |